[1] https://www.bicycling.com/rides/a20039883/9-ways-to-make-bik...
[2] https://www.bicycling.com/news/a23508352/netherlands-cellpho...
I'm fortunate that I don't sweat very much, my commute is only 4 miles each way, and I can tailor my schedule around the weather. So I start out early before the sun has cleared the trees, and ride slowly. As a result I'm not particularly sweaty when I arrive at work. Also, I have a casual-dress job with no public interaction.
I live on a street that happens to be a preferred route for cyclists commuting to and from the downtown area. So I see a lot of people on bikes. Most of the commuters are in fact just wearing normal street clothes. I don't even own any cycling-specific clothing.
I’m sure roadies dress that way in the Netherlands.
The difference is that US cyclists are mostly roadies because you need to really want to bike to do so, which in the Netherlands roadies are a minority of cyclists because it’s just the normal way to move around.